Transmitter element



Feb. 18, 1930. L. H. RICHMOND 1,747,265

TRANSMI TTER ELEMENT Filed March 29, 1928 I /4 E i; Z7

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Patented Feb. 18, 1930 UNITED STATES TRANSMITTER ELEMENT Applicationfiled March 29, 1928. Serial No. 265,670.

bratory diaphragm of a transmitter that will result in the maximumamplification of the effect of the movement of the diaphragm or any partof the electromagnetic device.

Another object is to avoid distortion in the electrical circuit by soconstructing the electromagnetic element that none of the parts willhave natural periods of vibration.

With the foregoing and other objects in view, the invention consists inthe combination of parts and in the details of construction hereinafterdescribed, certain embodiments thereof being illustrated in theaccompanying drawings, in which:

Fig. 1 is a side elevation of the device (re moved from the housing)shown attached to a diaphragm.

Fig. 2 is a detail view in elevation of the thrust lever.

Fig. 3 is a detail view in perspective of the pivot post.

Fig. 4 is a view in elevation of the pivot post with a coil of wirewound around same, and with the rocker arm pivoted thereon.

Referring more particularly to the drawings, there is shown in Fig. 1 asubstantially U-shaped magnetic frame 1 with an upper arm 2 and a lowerarm 3. Fig. 3 shows a pivot post i which is wound with many turns ofwire 13 which is adapted to carry an electric current thus making it asource of electromagnetic lines of force. The pivot post is made ofmagnetic material such as iron or preferably a good grade of highsilicon transformer steel.

The pivot post 4 is attached to the frame 1 by means of the screw bolt22 with the two legs 4 straddling the frame. The interior screw threadsin the post to receive the bolt 22 are shown in dotted lines at 11. Forpurposes of clarity the windings 13 are omitted in the showing inFig. 1. On the upper end of the post a is pivotally supported betweenthe two legs I a rocker arm 5 which is attached to the post 4: by bolts12 engaging the rocker arm and passing through the apertures 10 in thelegs 4 of the post. The rocker arm 5 is accurately balanced and isessentially an armature in its operation, as it is made of the magneticmaterial as the pivot post.

The rocker arm has rigidly fastened thereto a thrust lever 14 by meansof screw bolts 8 and loclrnuts 9. A thrust arm 17 is also provided fortransmitting motions of the diaphragm 20 to the thrust lever 14:. Thisis accomplished by passing the screw threads 17 through the upright 16of the thrust lever, and the screw threads 17* at the other extremity ofthe thrust arm into the barrel 19 of the diaphragm 20. This connectionbetween the thrust lever and the thrust arm is made adjustable, by meansof nuts 18 on either side of the upright 16, in order that the effectivelength of the arm 17 may be varied at will. The thrust arm is made ofnon-magnetic material.

A relative adjustment of the thrust lever and thrust arm varies theclearances 21 between the contact end 7 of the rocker arm 5 and the arm3 of the frame 1, and that between end 6 of the rocker arm and the arm 2of the frame 1. This clearance is preferably .004 inch. A coating ofvarnish or shellac is applied to the adjoining parts of the frame andthe rocker arm in order to prevent them from coming into actual metalliccontact at any time. It is sometimes desirable to fill this space withspongy rubber which holds the parts in correct relation to each otherwith out preventing their vibration.

In the operation of the device, a small energizing direct current iscaused to flow in the winding on the pivot post a by the use of asuitable source of electromagnetic force. This current in the windingcauses an electromagnetic field to be set up, this field having a singlepath in the pivot post, from which it divides into two paths ofapproximately equal length, one part passing through one side of therocker arm, through the air gap 21 betweenthe rocker arm 5 and theframe,

and thence through that side of the frame back to the pivot post 4. Theother path is symmetrically the same. The strength of this magneticcircuit is determined by the number of turns of wire in the winding, bythe strength of the current flowing therein, and by the reluctance inthe magnetic field. The greatest part of the reluctance in the magneticfield is caused by the air gaps 21 between the ends 6 and 7 of therocker arm 5 and the ends 2 and 3 respectively of the frame 1. Anyvariation in the length of these air gaps greatly changes the reluctanceof the circuit and hence causes a correspondingly large change in themagnetic flux through the windings. Changes in the magnetic flux causesinduced electromagnetic forces in the windings. The variations in theair gaps are in exact response to the sound which causes the diaphragmto move, which movement is communicated by means of the thrust arm andlever. Thus the varying electromagnetic force in the windings are causedby and are exactly similar to the varying pressures of the sound waves,which result is the object of the apparatus.

IVhile there has been shown and described a specific type of apparatus,it is not the purpose to so limit the invention, as variations of theparticular apparatus are possible within the scope of the proposedinvention, such as a Variation in the shape and size of any or all partsof the device; the placing of the Winding 13 on other parts of themagnetic circuit; the splitting of the winding into two or more parts,which may be put at various places in the magnetic circuit; the use of apermanent magnet to establish the magnetic field. This could be therocker arm or any part of the frame. A permanent magnet may also'be usedin any part of the circuit in addition to the use of the windings toestablish a magnetic field, each contributing its part.

I claim:

1. In a telephonic transmitter, a vibratory diaphragm, an electromagnetcomprising an angular frame with vertically staggered extremities and awire wound pivot post supported by said frame, an armature comprising arocker arm which is pivotally mounted on said pivot post and inoverlapping and spaced relation to the opposite sides of the staggeredends of said frame, a lever arm se cured to said rocker arm, a screwthreaded rod connecting said lever and rocker arm to said diaphragm forimparting movements of said diaphragm to said rocker arm, and adjustmentnuts on said rod for maintaining the adjustment thereof and theconsequent clearance between the rocker arm and the extremities of theframe.

2. In a telephonic transmitter, a diaphragm, an electromagnet comprisinga frame and a wire wound post secured thereto, an armature pivoted onsaid post with a clearance between said armature and said frame, a screwthreaded rod connecting said lever and armature to said diaphragm forimparting movements of said diaphragm to said armature, and adjustmentnuts on said rod for maintaining the adjustment thereof and of the airgap between said armature and said frame.

3. In a telephonic transmitter, a diaphragm, an electromagnet comprisinga frame and a wire wound post secured thereto, an armature pivoted onsaid post, an adj ust able lever and arm connecting said diaphragm withsaid armature for adjusting the relative spaced relation between saidarmature and said frame.

4. In a telephonic transmitter, a diaphragm, an electromagnet comprisinga frame and a wire wound post secured thereto, an armature pivoted onsaid post, adjustable means connecting said diaphragm, and adapt- LEONI-I. RICHMOND.

